Tumblr has kept mum on the cause of this downtime. “We’re working quickly to recover from a major issue in one of our database clusters. We’re incredibly sorry for the inconvenience,” the company said on Twitter.

“What has Tumblr been doing with all that money? Buying kittens?” a Tumblr user recently asked in frustration at finding the site unavailable.

“We use the kittens to power the servers,” replied Mark Coatney, media liaison at Tumblr, a former Newsweek editor who created the behind-the-scenes Newsweek blog that made Tumblr trendy with journalists.

Those kittens have a big job: Tumblr’s pageviews have increased 1,500 percent in the past year. We shudder to think what may have happened to them this time.

Tumblr went down because of a scheduled maintenance that “went haywire,” Tumblr Founder David Karp tells TechCrunch, forcing the engineers to take down a critical database cluster. Tumblr has been manually rebuilding the cluster all night and the service will be upas soon as possible, he said.